Hybrid metallic/composite joint with separate internal bearing

ABSTRACT

A metallic-composite joint fitting is provided. The fitting may comprise a frustoconical internal bearing having a bore, a conical sleeve configured to be disposed about the frustoconical internal bearing, a composite structure configured to couple between the frustoconical internal bearing and the conical sleeve, a metallic end fitting configured to be disposed within the bore and couple to the frustoconical internal bearing, and an external nut configured to couple to the metallic end fitting and the conical sleeve, wherein at least one of the frustoconical internal bearing or the conical sleeve comprises a flanged portion mutually configured to couple the conical sleeve to the frustoconical internal bearing via a locking ring.

FIELD

The present disclosure relates to composite tube assemblies and methodsof manufacture of composite tube assemblies, and, more specifically, toaircraft retractable landing gear systems having metallic componentinterfaces to composite tubes.

BACKGROUND

Composite tubes are often used due to their high strength and low weightin industries and applications where weight is a significant designfactor, such as in the aircraft and automotive industries. Landing gearsupports an aircraft while the aircraft is on the ground and tend tocomprise metallic components capable of withstanding the high structuralloads environment of aircraft landing. Landing gear may include one ormore wheels and a shock strut assembly in order to attenuate the forcesassociated with landing or ground operations. Composite tubes may beused to interface between metallic structures and thereby tend to reducecomponent weight. The structures may be subjected to axial tensile andcompressive loads, shear loads, bending loads, and torsional loads.Working loads may be transmitted directly through to the compositestructure which may benefit of a connector having an optimized load pathbetween metallic structures and the composite structure.

SUMMARY

In various embodiments, a metallic-composite joint fitting is providedcomprising a frustoconical internal bearing having a bore, a conicalsleeve configured to be disposed about the frustoconical internalbearing, a composite structure configured to couple between thefrustoconical internal bearing and the conical sleeve, a metallic endfitting configured to be disposed within the bore and couple to thefrustoconical internal bearing, and an external nut configured to coupleto the metallic end fitting and the conical sleeve, wherein at least oneof the frustoconical internal bearing or the conical sleeve comprises aflanged portion mutually configured to couple the conical sleeve to thefrustoconical internal bearing via a locking ring.

In various embodiments, the joint fitting further comprises an internalbolt coupled within the bore, wherein the metallic end fitting comprisesa bearing portion configured to be disposed within the bore and coupleto the internal bolt. In various embodiments, the composite structurecomprises a cylindrical portion and a conical end portion. In variousembodiments, the conical end portion is coupled relatively between thefrustoconical internal bearing at a first conical bearing surface andthe conical sleeve at a second conical bearing surface. In variousembodiments, the conical end portion is flared. In various embodiments,the bearing portion contacts the frustoconical internal bearing at acylindrical bearing surface. In various embodiments, the internal boltis integral to the frustoconical internal bearing. In variousembodiments, the metallic end fitting is coupled to the internal bolt atan internally threaded surface of the metallic end fitting. In variousembodiments, the external nut is contacted with the conical sleeve viaan end washer. In various embodiments, the conical sleeve comprises theflanged portion coupled to the frustoconical internal bearing via thelocking ring.

In various embodiments, a landing gear system is provided comprising ashock strut coupled to an axle, a wheel coupled to the axle, and ametallic-composite joint fitting comprising a frustoconical internalbearing, an internal bolt coupled within a bore of the frustoconicalinternal bearing, a metallic end fitting coupled to the internal bolt,wherein the metallic end fitting comprises a bearing portion disposedwithin the bore, a conical sleeve disposed about the frustoconicalinternal bearing, and an external nut coupled to the metallic endfitting and the conical sleeve, wherein the conical sleeve comprises aflanged portion coupled to the frustoconical internal bearing.

In various embodiments, a composite structure is coupled between thefrustoconical internal bearing and the conical sleeve. In variousembodiments, the composite structure comprises a cylindrical portion anda conical end portion. In various embodiments, the conical end portionis coupled relatively between the frustoconical internal bearing at afirst conical bearing surface and the conical sleeve at a second conicalbearing surface. In various embodiments, the conical end portion isflared. In various embodiments, the bearing portion contacts thefrustoconical internal bearing at a cylindrical bearing surface. Invarious embodiments, the internal bolt is integral to the frustoconicalinternal bearing. In various embodiments, the metallic end fitting iscoupled to the internal bolt at an internally threaded surface of themetallic end fitting. In various embodiments, the flanged portion of theconical sleeve is coupled to the frustoconical internal bearing via alocking ring.

In various embodiments, a method of joining a composite structure and ametallic end fitting comprises coupling an internal bolt within a boreof a frustoconical internal bearing, wrapping the composite structureover the frustoconical internal bearing to form a conical end portion,disposing a conical sleeve over the conical end portion to enclose theconical end portion between a first conical bearing surface and a secondconical bearing surface, inserting a bearing portion of the metallic endfitting into the bore of the frustoconical internal bearing and couplingthe internal bolt to an internally threaded surface of the metallic endfitting, and coupling an external nut to an externally threaded surfaceof the metallic end fitting and contacting the external nut with theconical sleeve.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the figures, wherein like numerals denotelike elements.

FIG. 1 illustrates an aircraft, in accordance with various embodiments;

FIG. 2 illustrates a metallic-composite joint fitting, in accordancewith various embodiments;

FIG. 3 illustrates load paths in a metallic-composite joint fitting, inaccordance with various embodiments; and

FIG. 4 illustrates a method of joining a composite structure and ametallic end fitting, in accordance with various embodiments.

DETAILED DESCRIPTION

All ranges and ratio limits disclosed herein may be combined. It is tobe understood that unless specifically stated otherwise, references to“a,” “an,” and/or “the” may include one or more than one and thatreference to an item in the singular may also include the item in theplural.

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice theexemplary embodiments of the disclosure, it should be understood thatother embodiments may be realized and that logical changes andadaptations in design and construction may be made in accordance withthis disclosure and the teachings herein. Thus, the detailed descriptionherein is presented for purposes of illustration only and notlimitation.

The scope of the disclosure is defined by the appended claims and theirlegal equivalents rather than by merely the examples described. Forexample, the steps recited in any of the method or process descriptionsmay be executed in any order and are not necessarily limited to theorder presented. Furthermore, any reference to singular includes pluralembodiments, and any reference to more than one component or step mayinclude a singular embodiment or step. Also, any reference to attached,fixed, coupled, connected or the like may include permanent, removable,temporary, partial, full and/or any other possible attachment option.Additionally, any reference to without contact (or similar phrases) mayalso include reduced contact or minimal contact. Surface shading linesmay be used throughout the figures to denote different parts but notnecessarily to denote the same or different materials.

With reference to FIG. 1, an aircraft 10 in accordance with variousembodiments may comprise aircraft systems, for example, one or morelanding gear such as landing gear 12, landing gear 14 and landing gear16. Landing gear 12, landing gear 14 and landing gear 16 may generallysupport aircraft 10 when aircraft 10 is not flying, allowing aircraft 10to taxi, take off, and land without damage and may comprise wheels andan oleo strut, also referred to as a shock strut, comprising a strutcylinder and a strut piston filled with a hydraulic fluid. For example,landing gear 12 may include wheels 18 coupled by an axle 20 and a shockstrut assembly 22 comprising a metallic-composite joint fitting 200.

In various embodiments and with additional reference to FIG. 2,metallic-composite joint fitting 200 (hereinafter “fitting”) isillustrated in planar cross section of the XY-plane. Fitting 200comprises a coupling between a metallic end fitting 202 and a compositestructure 204. Composite structure 204 comprises a conical end portion206 wrapped about a frustoconical internal bearing 208. In this regard,the conical end portion 206 may engage with the frustoconical internalbearing 208 along a first conical bearing surface 210. In variousembodiments, the conical end portion 206 of the composite structure 204may flare outward from the first conical bearing surface 210. Statedanother way, the conical end portion 206 may increase in radial (i.e.,X-axis) thickness, as compared to the radial thickness of a cylindricalportion 207 of the composite structure 204, progressing along the Y-axisfrom the cylindrical portion 207 toward the tip of the conical endportion 206.

In various embodiments, the metallic end fitting 202 may comprise ashaft 212 and a coupling feature 214. The coupling feature 214 includesan externally threaded surface 216 at the outer diameter of the couplingfeature 214 configured to engage with an external nut 220. Theexternally threaded surface 216 extends from the shaft 212 toward abearing portion 218 relatively below (along the Y-axis) the externallythreaded surface 216. The bearing portion 218 is inserted into a bore222 through the frustoconical internal bearing 208 and engages with acylindrical bearing surface 224 which defines the inner diameter of thefrustoconical internal bearing 208. The coupling feature 214 includes aninternally threaded surface 226 at the inner diameter of the couplingfeature 214. In various embodiments, the internally threaded surface 226may extend along the inner diameter of the coupling feature 214 radiallyinward of the bearing portion 218. The internally threaded surface 226may be configured to engage with a shank 228 of an internal bolt 230.

Internal bolt 230 may extend into bore 222 of the frustoconical internalbearing 208. In various embodiments, the head 232 of internal bolt 230may seat against a shoulder 234 within the bore 222 and thereby tend toinhibit the metallic end fitting 202 from translating axially outward(along the Y-axis) with respect to the frustoconical internal bearing208 and maintain the engagement of the bearing portion 218 along thecylindrical bearing surface 224. In various embodiments, the head 232 ofinternal bolt 230 may be configured to inhibit rotation of the internalbolt with respect to the frustoconical internal bearing 208. Forexample, head 232 may be relatively D-shaped and the bore 222 mayinclude a relatively flat portion configured to interface with a flatportion of the D-shaped head tending thereby to inhibit rotation of theinternal bolt 230 with respect to the frustoconical internal bearing208. In various embodiments, an internal bolt may be integral to afrustoconical internal bearing or may be fixedly coupled to afrustoconical internal bearing such as, for example, by welding orbonding.

In various embodiments, a conical sleeve 236 may be disposed about thefrustoconical internal bearing 208 over the conical end portion 206 ofthe composite structure 204. Conical sleeve 236 comprises a flangedportion 237 in contact with the conical end portion 206. The conicalsleeve 236 may lie radially outward of the conical end portion 206 andthe frustoconical internal bearing 208 may lie radially inward of theconical end portion 206 and the conical sleeve 236. In this regard, theconical end portion 206 may be sandwiched between the frustoconicalinternal bearing 208 at first conical bearing surface 210 and theconical sleeve 236 at a second conical bearing surface 238. In variousembodiments, external nut 220 may be contacted with the conical sleeve236, the conical end portion 206, and the frustoconical internal bearing208 via an end washer 240. In various embodiments, the flanged portion237 may be configured to interface between the external nut 220 and/orthe end washer 240 and the conical end portion 206.

In this regard, the external nut 220 tends to inhibit the metallic endfitting 202 from translating axially inward (along the Y-axis) withrespect to the frustoconical internal bearing 208 by generating aninterference at the second conical bearing surface 238 between theconical sleeve 236 and the conical end portion 206. In variousembodiments, the conical sleeve may be coupled to the frustoconicalinternal bearing 208 such as by a locking ring 239. In this regard, thefrustoconical internal bearing 208 and the conical sleeve 236 may tendto behave as a monolithic structure when distributing loads such as, forexample, bending loads. Stated another way, the locking ring 239 andflanged portion 237 may tend to inhibit relative motion between theinternal bearing 208 and the conical sleeve 236 in response to bendingloads. In various embodiments, the locking ring 239 may be integral withthe internal bearing 208. In various embodiments, the conical sleeve 208may comprise two or more sections fitted about the locking ring 239 andcoupled to the conical end portion 206 such as, for example, by a clampband or by welding between the sections.

In various embodiments and with additional reference to FIG. 3, fitting200 may be optimized to carry compressive and tension loads via threadedsurfaces while carrying bending loads at non-threaded bearing surfaces.In this regard, fitting 200 may tend to benefit of improved bending loadperformance. Fitting 200 is illustrated in cross section overlaid withoptimized load paths 300 for axial tension, axial compression, andradial bending loads applied at metallic end fitting 202. A compressiveforce F_(C) applied at the metallic end fitting 202 travels as shown byarrows 302 through externally threaded surface 216 into external nut220. External nut 220 transmits F_(C) through end washer 240 intoconical sleeve 236. The conical sleeve 236 transmits the compressiveforce F_(C) through the second conical bearing surface 238 into theconical end portion 206 and thereby the cylindrical portion 207 ofcomposite structure 204. As shown by arrows 304, a tension force FTapplied at the metallic end fitting 202 is transmitted via internallythreaded surface 226 into shank 228 of internal bolt 230. Internal bolt230 transmits the tension force FT through shoulder 234 intofrustoconical internal bearing 208. The frustoconical internal bearing208 passes the tension force FT through the first conical bearingsurface 210 into the conical end portion 206 and thereby the cylindricalportion 207 of composite structure 204.

A bending load F_(B) is applied at the metallic end fitting 202 andtravels as shown by arrow 306 entirely (i.e., greater than 95% of thebending load) through cylindrical bearing surface 224 into thefrustoconical internal bearing 208. The frustoconical internal bearing208 passes the bending load through locking ring 239 and flanged portion237 and through the first conical bearing surface 210 into the conicalend portion 206. Head 232 of internal bolt 230 may have relativelyreduced diameter in comparison to the diameter of the bore 222 andthereby engage primarily axially (along the Y-axis) the frustoconicalinternal bearing 208 at the shoulder 234. In this regard, radial contact(along the X-axis) between the frustoconical internal bearing 208 andthe head 232 under a bearing load may be minimized or eliminated. Thefitting 200 may thereby tend to inhibit bearing loads from passingthrough any of the threaded surfaces (226, 216). In response to bendingload F_(B) applied at the metallic end fitting 202 shear loads (alongthe Y-axis) may be induced at the locking ring 239 which are transferredinto the flanged portion 237 of conical sleeve 236 and into thefrustoconical internal bearing 208. In this regard, the shear loadbehavior of the locking ring 239 in response to the bending load F_(B)tends to impart the monolithic behavior of the conical sleeve 236 andthe frustoconical internal bearing 208 in bending by restriction ofrelative motion (generating the shear loads) between the conical sleeve236 and the frustoconical internal bearing 208. Stated another way, themonolithic behavior induced by the locking ring 239 squeezes the conicalend portion 206 between the conical sleeve 236 and the frustoconicalinternal bearing 208 in response to the bending load F_(B).

In various embodiments, a method 400 of joining a composite structure204 and a metallic end fitting 202 may comprise coupling an internalbolt 230 within a bore 222 of a frustoconical internal bearing 208 (step402). Method 400 includes wrapping the composite structure 204 over thefrustoconical internal bearing 208 to form a conical end portion 206(step 404). Method 400 includes disposing a conical sleeve 236 over theconical end portion 206 to enclose the conical end portion 206 between afirst conical bearing surface 210 and a second conical bearing surface238 (step 406). Step 406 includes coupling a flanged portion 237 of theconical sleeve 236 to the frustoconical internal bearing 208 via alocking ring 239. Method 400 includes inserting a bearing portion of themetallic end fitting 202 into the bore of the frustoconical internalbearing 208 and coupling the internal bolt 230 to an internally threadedsurface 226 of the metallic end fitting 202 (step 408). Method 400includes coupling an external nut 220 to an externally threaded surface216 of the metallic end fitting 202 and contacting the external nut 220with the flanged portion 237 of the conical sleeve 236 (step 410). Invarious embodiments, the external nut 220 may be contacted with theflanged portion 237 of conical sleeve 236 via an end washer 240.

Benefits and other advantages have been described herein with regard tospecific embodiments. Furthermore, the connecting lines shown in thevarious figures contained herein are intended to represent exemplaryfunctional relationships and/or physical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical connections may be present in apractical system. However, the benefits, advantages, and any elementsthat may cause any benefit or advantage to occur or become morepronounced are not to be construed as critical, required, or essentialfeatures or elements of the disclosure. The scope of the disclosure isaccordingly to be limited by nothing other than the appended claims, inwhich reference to an element in the singular is not intended to mean“one and only one” unless explicitly so stated, but rather “one ormore.” Moreover, where a phrase similar to “at least one of A, B, or C”is used in the claims, it is intended that the phrase be interpreted tomean that A alone may be present in an embodiment, B alone may bepresent in an embodiment, C alone may be present in an embodiment, orthat any combination of the elements A, B and C may be present in asingle embodiment; for example, A and B, A and C, B and C, or A and Band C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “various embodiments,” “oneembodiment,” “an embodiment,” “an example embodiment,” etc., indicatethat the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described. After reading the description, itwill be apparent to one skilled in the relevant art(s) how to implementthe disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is invoke 35 U.S.C. 112(f) unlessthe element is expressly recited using the phrase “means for.” As usedherein, the terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus.

What is claimed is:
 1. A metallic-composite joint fitting, comprising: afrustoconical internal bearing having a bore; a conical sleeveconfigured to be disposed about the frustoconical internal bearing; acomposite structure configured to couple between the frustoconicalinternal bearing and the conical sleeve; a metallic end fittingconfigured to be disposed within the bore and couple to thefrustoconical internal bearing, wherein the metallic end fittingcomprises a bearing portion configured to be disposed within the bore;and an external nut configured to couple to the metallic end fitting andthe conical sleeve, wherein at least one of the frustoconical internalbearing or the conical sleeve comprises a flanged portion mutuallyconfigured to couple the conical sleeve to the frustoconical internalbearing via a locking ring.
 2. The metallic-composite joint fitting ofclaim 1, further comprising an internal bolt coupled within the bore,wherein the metallic end fitting is coupled to the internal bolt.
 3. Themetallic-composite joint fitting of claim 2, wherein the compositestructure comprises a cylindrical portion and a conical end portion. 4.The metallic-composite joint fitting of claim 3, wherein the conical endportion is coupled relatively between the frustoconical internal bearingat a first conical bearing surface and the conical sleeve at a secondconical bearing surface.
 5. The metallic-composite joint fitting ofclaim 4, wherein the conical end portion is flared.
 6. Themetallic-composite joint fitting of claim 1, wherein the bearing portioncontacts the frustoconical internal bearing at a cylindrical bearingsurface.
 7. The metallic-composite joint fitting of claim 1, wherein theinternal bolt is integral to the frustoconical internal bearing.
 8. Themetallic-composite joint fitting of claim 1, wherein the metallic endfitting is coupled to the internal bolt at an internally threadedsurface of the metallic end fitting.
 9. The metallic-composite jointfitting of claim 1, wherein the external nut is contacted with theconical sleeve via an end washer.
 10. The metallic-composite jointfitting of claim 1, wherein the conical sleeve comprises the flangedportion coupled to the frustoconical internal bearing via the lockingring.
 11. A landing gear system, comprising: a shock strut coupled to anaxle; a wheel coupled to the axle; and a metallic-composite jointfitting, comprising: a frustoconical internal bearing; an internal boltcoupled within a bore of the frustoconical internal bearing; a metallicend fitting coupled to the internal bolt, wherein the metallic endfitting comprises a bearing portion disposed within the bore; a conicalsleeve disposed about the frustoconical internal bearing; and anexternal nut coupled to the metallic end fitting and the conical sleeve,wherein the conical sleeve comprises a flanged portion coupled to thefrustoconical internal bearing.
 12. The landing gear system of claim 11,wherein a composite structure is coupled between the frustoconicalinternal bearing and the conical sleeve.
 13. The landing gear system ofclaim 12, wherein the composite structure comprises a cylindricalportion and a conical end portion.
 14. The landing gear system of claim13, wherein the conical end portion is coupled relatively between thefrustoconical internal bearing at a first conical bearing surface andthe conical sleeve at a second conical bearing surface.
 15. The landinggear system of claim 14, wherein the conical end portion is flared. 16.The landing gear system of claim 11, wherein the bearing portioncontacts the frustoconical internal bearing at a cylindrical bearingsurface.
 17. The landing gear system of claim 11, wherein the internalbolt is integral to the frustoconical internal bearing.
 18. The landinggear system of claim 11, wherein the metallic end fitting is coupled tothe internal bolt at an internally threaded surface of the metallic endfitting.
 19. The landing gear system of claim 11, wherein the flangedportion of the conical sleeve is coupled to the frustoconical internalbearing via a locking ring.
 20. A method of joining a compositestructure and a metallic end fitting, comprising: coupling an internalbolt within a bore of a frustoconical internal bearing; wrapping thecomposite structure over the frustoconical internal bearing to form aconical end portion; disposing a conical sleeve over the conical endportion to enclose the conical end portion between a first conicalbearing surface and a second conical bearing surface and coupling aflanged portion of the conical sleeve to the frustoconical internalbearing; inserting a bearing portion of the metallic end fitting intothe bore of the frustoconical internal bearing and coupling the internalbolt to an internally threaded surface of the metallic end fitting; andcoupling an external nut to an externally threaded surface of themetallic end fitting and contacting the external nut with the flangedportion of the conical sleeve.